Organic photovoltaic cells are considered a promising solar cell technology because of the configurability of electronic and optical properties of organic semiconductors and the potential for low-cost roll-to-roll manufacturing. However, the relatively low efficiency of organic solar cells is a major roadblock that stands in the way of commercialization.
Efficiencies of organic photovoltaic cells may be improved by stacking several individual cells having different optical gaps which are combined into a series-connected stack. The cells are tuned so some photons that have energy sufficient to pass through a first one of the stacked cells can be absorbed by other ones of the stacked cells. Conventionally, the stacked cells are electrically interconnected in series in the stack. As a result of the series connected arrangement, current passing through the cells is limited to the smallest current produced by one of the cells in the stack. Efficient cells that produce a lot of current are limited by inefficient cells that produce little current. To avoid this scenario, stacked cells are generally matched so the cells in a stack each produce approximately an equivalent current. Such matching can be time consuming and expensive.
Further, the manufacture of organic photovoltaic cells is complicated by current processes of fabricating conductive electrodes. Previous methods for depositing transparent conductive films on a photovoltaic cell to form an electrode involve high temperature, vacuum sputtering processes, and harsh chemicals, which can damage organic photovoltaic cells.
One or more embodiments may address one or more of the above issues.